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2 Mar 2021

Nutrition: helping farmers in the pre and post-weaning periods

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Phil Elkins

Job Title



Nutrition: helping farmers in the pre and post-weaning periods

Over the past decade or so, youngstock has become increasingly at the forefront of the dairy vet-farmer relationship. This is primarily due to an awareness from both the farming and veterinary sectors of the potential gains associated with improved youngstock performance.

These gains can be both overt and obvious, such as through reduced youngstock morbidity and mortality, and covert with a long time to return on investment, such as through improved first and subsequent lactation performance.

The impact of improved youngstock performance will influence animal health, welfare, productivity and – hopefully – profitability for our clients.

However, much of the emphasis historically has been on the peripartum period, with particular attention to ensuring adequate passive transfer of immunity and early-life nutrition. This is for good reason, with substandard performance relatively commonplace across the industry – and widely published – with more than a quarter of calves born failing to reach adequate passive transfer1.

In the author’s experience, many farms are now dedicating more time and resources to successful calf rearing, with improvements in calf morbidity, mortality and growth rates.

With regards to the next management period in a calf’s life – weaning – a wide range of practices are still evident throughout the UK dairy herd, with an associated disparity in performance, with consequences for animal health and production.

It is not unusual to see heifers that have achieved excellent daily liveweight gains during the milk feeding period suffer from a period of no growth and increased disease around weaning – and this represents an opportunity for vets to engage further with their clients for a mutual benefit.

During the milk feeding period, a degree of uniformity exists around procedures, or certainly a limited number of options or approaches – for example, milk or commercial milk replacer is usually fed either once a day, twice a day or through an automated feeding system. This allows research to be undertaken with a degree of relevance to most producers.

The same degree of uniformity is not present with preweaning and post-weaning diets and management; as such, most research is not directly comparable with individual farm situations.

That is not to belittle the research or dismiss its importance – for a vet to have the best impact on weaning success requires a balance between research, first principles, experience and a logical approach.

Present performance

The first step in looking to help farmers achieve successful weaning is to quantify the present performance.

Two main indicators of weaning performance exist – average daily liveweight gain (DLWG) in the peri‑weaning period and disease rates around this time.

The DLWG should be estimated at a group level by weighing a cohort of calves at two weeks preweaning, then weighing the same calves again at two weeks and six weeks post-weaning. Then a simple calculation will give a group average DLWG around weaning, together with an indication of spread within the group.

Obviously, this should be contextualised against preweaning growth rates and required growth rates. Required growth rates should consider target age at first service of 13 months at 65% of mature (third calver) adult weight.

A failure to achieve adequate growth rates in the peri‑weaning period indicates lost productivity at a time when feed conversion efficiency is most in the favour of the farmer.

When faced with a growth check (or even growth loss) around weaning, first principles are key. When you consider the changes that occur around weaning, those that affect growth rates can be separated into two categories – dietary risks and management risks.

Pre-weaning, most calves will have three main components to their diet – milk or commercial milk replacer (milk), a forage source and a concentrate source:

  • The milk will be providing a major portion of their energy requirements, bypassing the rumen for abomasal digestion.
  • The forage will be providing a medium for rumen microbes, and is important for prevention of subacute rumen acidosis and development of ruminal papillae2.
  • Concentrates are important for development of rumen size to drive intakes.

Post‑weaning diet will generally consist of a forage source and a concentrate source.

To intake the same amount of energy to maintain growth, the forage intake must increase rapidly, with moderate increases in concentrates to replace the energy provision from the milk.

Milk is approximately 22.7 megajoules of energy per kilogram dry matter (MJ/kg) – with intakes preweaning of up to 8 litres, this equates to around 20MJ of energy. If the forage of choice is straw, at around 6MJ/kg to 7MJ/kg, this equates to the calves eating 3kg dry matter more straw post-weaning.

Milk and calf milk replacer (CMR) are also reliable sources of both minerals and vitamins required for growth, immunity and health. This supply must also be adequately maintained post-weaning.

CMR is supplemented with trace minerals. Post‑weaning, a risk exists that supply of these trace minerals is not maintained. In particular, this relates to diets based on forage alone, or forage and straights rather than a mineralised concentrate feed.

In these circumstances, it is worth considering whether mineral supplementation would be beneficial and, if so, the most appropriate route.

Management risks

The management risks associated with dietary insufficiency in the peri‑weaning period are no different from at any other time during the animal’s life; however, the consequences can be far more severe.

These animals are having a large, enforced dietary change to negotiate while still having large requirements for growth, immunity and organ development.

The increase in respiratory disease post-weaning is a result of immune suppression and challenges around post‑weaning management.

The immune suppression occurs due to four main risk factors:

  • transition between maternally derived and innate immunity
  • dietary challenges, as previously mentioned
  • the inherent stress associated with weaning
  • stressors associated with management

Post-weaning management is often very different from preweaning management. This is associated with a risk of reduced dry matter intake and successful dietary transition, immune suppression and increased pathogenic challenge.

The following list is an indication of some of the management changes that can occur around weaning with potentially negative effects (but is certainly not comprehensive):

  • change from individual or paired housing to group housing
  • changes of management groups
  • mixing airspace with other age groups
  • surgical interventions – castrations and disbudding
  • feed presentation and availability
  • feed constituents
  • water availability

Opportunity

So, having quantified current performance on a unit through assessing DLWG and morbidity rates in the post‑weaning period, an opportunity is often presented for vets to engage with their clients to improve the situation.

This advice often forms part of a journey of improvement for the unit, rather than initially targeting perfection as ever.

A successful weaning period relies on the following:

  • preparation for weaning
  • minimising stress around weaning time
  • appropriate dietary provision
  • optimising management

One of the main factors of preparation for weaning is to ensure calves are provided with adequate nutrition to promote health and growth preweaning. However, calves on an accelerated growth plane preweaning – associated with large volumes of milk intakes – fail to transition quickly to solid feeds, with reduced dry matter intake and increased non‑nutritional oral behaviours associated with stress.

However, once weaning has successfully been achieved, these animals demonstrate less disease and a quicker recovery when challenged with respiratory pathogens – so it would appear an accelerated growth in the milk feeding period, together with a smooth transition, would facilitate optimum growth and immunity3.

The past decade has seen more interest in – and uptake of – once-daily milk feeding during the second half of the milk feeding period (from 28 days). Once a day obviously offers a management and labour benefit, but also health benefits.

Once-daily fed calves – when compared with twice‑daily fed calves – consume more solid feed prior to calving, which aids with the transition to solid feed at weaning. They also have lower stress markers in the lead-up to weaning4.

The process of weaning is important to consider – reducing milk provision for 10 days to 2 weeks prior to weaning, rather than abrupt weaning, is associated with reduced DLWG in the preweaning period, but increased starter and forage intakes both before and after weaning, leading to increased growth rates post-weaning, and an overall increase in feed conversion efficiency and growth rates5.

So, it would appear the best preparation for weaning is a shift to once-daily feeding and a gradual weaning strategy.

From a dietary perspective, it is essential to minimise the drop in dry matter intake. This is best achieved through consistency of dietary ingredients – switching concentrate provision or forage around weaning is associated with a deeper and more prolonged drop in dry matter intake.

It is important to ensure this is suitable from a vitamin and mineral perspective – mineral deficiencies, such as rickets, when this is not considered can be disastrous.

Balance

Reducing stress around weaning is a balance between the limited science and bespoke advice. It is important to maintain as many factors of management around weaning for at least two weeks to minimise stress and reduce intakes.

Dry matter intakes are also improved for paired or grouped calves compared with single calves. This will vary between farms, but a suggested management around weaning may be as follows:

  • Castrate and disbud where needed, well before weaning.
  • Move to once-daily feeding from 28 days.
  • Pair or group calves from 42 days and gradually reduce milk feeding.
  • Wean when double birthweight and consuming an average of 2kg starter per calf per day.
  • Keep in same pair/group for two weeks with same concentrate and forage ad lib – ensure vitamin and mineral provision.
  • Move to small group (maximum 20) from two weeks post‑weaning.
  • From this point, can gradually transition concentrate and forage provision.
  • At all stages, ensure ad lib food and water provision, with adequate trough space and presentation of fresh, palatable, clean nutrients.

Summary

In summary, by looking at weaning performance, and quantifying DLWG and morbidity, an opportunity exists for vets to engage with clients to improve health, welfare and productivity of their stock.

The approach will be necessarily bespoke, but based around minimising the drop in dry matter intakes, optimising immunity and minimising stress.

  • Vet Times (2021), Volume 51, Issue 8, Pages 6-7

References

  • MacFarlane JA, Grove-White DH, Royal MD and Smith RF (2015). Identification and quantification of factors affecting neonatal immunological transfer in dairy calves in the UK, Veterinary Record 176(24): 625.
  • Kim YH, Nagata R, Ohtani N, Ichijo T, Ikuta K and Sato S (2016). Effects of dietary forage and calf starter diet on ruminal pH and bacteria in Holstein calves during weaning transition, Frontiers in Microbiology 7: 1,575.
  • Hulbert LE and Moisá SJ (2016). Stress, immunity, and the management of calves, Journal of Dairy Science 99(4): 3,199-3,216.
  • Saldana DJ, Jones CM, Gehman AM and Heinrichs AJ (2019). Effects of once-versus twice-a-day feeding of pasteurized milk supplemented with yeast-derived feed additives on growth and health in female dairy calves, Journal of Dairy Science 102(4): 3,654-3,660.
  • Steele MA, Doelman JH, Leal LN, Soberon F, Carson M and Metcalf JA (2017). Abrupt weaning reduces postweaning growth and is associated with alterations in gastrointestinal markers of development in dairy calves fed an elevated plane of nutrition during the preweaning period, Journal of Dairy Science 100(7): 5,390-5,399.

Meet the authors

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Phil Elkins

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